You can find people on the Internet talking about "Scientific pitch notation (SPN), also known as American standard pitch notation (ASPN) and international pitch notation (IPN)", like on Wikipedia.
But if you try to Google the names for actual documents, official website, or standards bodies, they don't seem to exist. Does any know of an actual ISO standard or any type standard that supports all these websites' claims for the initialisms above?
Why is this question closed? The answer the closer linked to just points to a "source" which is the wikipedia article I quoted from, which has no official standards as a source. Wikipedia is not a source.
It also mentions a proposal in 1939, but that's hardly a standard, and certainly not a modern nor international one.
